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#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <features.h>
#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
#include <netpacket/packet.h>
#include <net/ethernet.h>
#else
#include <asm/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#endif
#include <errno.h>
#include "packet.h"
#include "debug.h"
#include "dhcpd.h"
#include "options.h"
void init_header(struct dhcpMessage *packet, char type)
{
memset(packet, 0, sizeof(struct dhcpMessage));
switch (type) {
case DHCPDISCOVER:
case DHCPREQUEST:
case DHCPRELEASE:
case DHCPINFORM:
packet->op = BOOTREQUEST;
break;
case DHCPOFFER:
case DHCPACK:
case DHCPNAK:
packet->op = BOOTREPLY;
}
packet->htype = ETH_10MB;
packet->hlen = ETH_10MB_LEN;
packet->cookie = htonl(DHCP_MAGIC);
packet->options[0] = DHCP_END;
add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
}
/* read a packet from socket fd, return -1 on read error, -2 on packet error */
int get_packet(struct dhcpMessage *packet, int fd)
{
int bytes;
int i;
const char broken_vendors[][8] = {
"MSFT 98",
""
};
char unsigned *vendor;
memset(packet, 0, sizeof(struct dhcpMessage));
bytes = read(fd, packet, sizeof(struct dhcpMessage));
if (bytes < 0) {
DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");
return -1;
}
if (ntohl(packet->cookie) != DHCP_MAGIC) {
LOG(LOG_ERR, "received bogus message, ignoring");
return -2;
}
DEBUG(LOG_INFO, "Received a packet");
if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
for (i = 0; broken_vendors[i][0]; i++) {
if (vendor[OPT_LEN - 2] == (unsigned char) strlen(broken_vendors[i]) &&
!strncmp(vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {
DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",
broken_vendors[i]);
packet->flags |= htons(BROADCAST_FLAG);
}
}
}
return bytes;
}
u_int16_t checksum(void *addr, int count)
{
/* Compute Internet Checksum for "count" bytes
* beginning at location "addr".
*/
register int32_t sum = 0;
u_int16_t *source = (u_int16_t *) addr;
while (count > 1) {
/* This is the inner loop */
sum += *source++;
count -= 2;
}
/* Add left-over byte, if any */
if (count > 0) {
/* Make sure that the left-over byte is added correctly both
* with little and big endian hosts */
u_int16_t tmp = 0;
*(unsigned char *) (&tmp) = * (unsigned char *) source;
sum += tmp;
}
/* Fold 32-bit sum to 16 bits */
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
/* Constuct a ip/udp header for a packet, and specify the source and dest hardware address */
int raw_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
u_int32_t dest_ip, int dest_port, unsigned char *dest_arp, int ifindex)
{
int fd;
int result;
struct sockaddr_ll dest;
struct udp_dhcp_packet packet;
if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
DEBUG(LOG_ERR, "socket call failed: %s", strerror(errno));
return -1;
}
memset(&dest, 0, sizeof(dest));
memset(&packet, 0, sizeof(packet));
dest.sll_family = AF_PACKET;
dest.sll_protocol = htons(ETH_P_IP);
dest.sll_ifindex = ifindex;
dest.sll_halen = 6;
memcpy(dest.sll_addr, dest_arp, 6);
if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
DEBUG(LOG_ERR, "bind call failed: %s", strerror(errno));
close(fd);
return -1;
}
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source_ip;
packet.ip.daddr = dest_ip;
packet.udp.source = htons(source_port);
packet.udp.dest = htons(dest_port);
packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
packet.ip.tot_len = packet.udp.len;
memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
packet.udp.check = checksum(&packet, sizeof(struct udp_dhcp_packet));
packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
packet.ip.ihl = sizeof(packet.ip) >> 2;
packet.ip.version = IPVERSION;
packet.ip.ttl = IPDEFTTL;
packet.ip.check = checksum(&(packet.ip), sizeof(packet.ip));
result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));
if (result <= 0) {
DEBUG(LOG_ERR, "write on socket failed: %s", strerror(errno));
}
close(fd);
return result;
}
/* Let the kernel do all the work for packet generation */
int kernel_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
u_int32_t dest_ip, int dest_port)
{
int n = 1;
int fd, result;
struct sockaddr_in client;
if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
return -1;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1)
return -1;
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(source_port);
client.sin_addr.s_addr = source_ip;
if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
return -1;
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(dest_port);
client.sin_addr.s_addr = dest_ip;
if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
return -1;
result = write(fd, payload, sizeof(struct dhcpMessage));
close(fd);
return result;
}
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